Lead/Lag Pumps 3

[shahyar]

Hi,
Can somebody explain what the lead/lag control means in pumps?(foe a novice)
How about HOA?
thanks

 

[schnipp]

HOA is hand-off-auto.

Hand is when you control it with pushbuttons usually near the pump.
Off is a controlled state so that the pump will not start (not to be used for working on the pump, then you need to lock it out!)
Auto is when the starting and stopping of said pump is controlled by a computer, PLC, remote operating system.

 

[cub3bead]

Lead-lag usually refers to the operation of duplex equipment such as sump pumps. The "lead" pump will be the first to start and the "lag" pump will be next if the liquid level continues to rise in the sump. Many of these installations include an alternator so that the "A" pump will be "lead" for one cycle and "lag" for the next. The intent here is to balance to the runtime of the pumps so that they wear equally, maximizing maintenace intervals.

However, when pumping abrasive materials in facilities with high cpacity factors such as coal fired powerplants, the alternator is sometimes diasbled on pumps in ash water service. The theory is when the "lead" pump wears out the plant can continue to operate with the "lag" pump with minimal wear while the worn out pump is repaired or replaced. This requires plant personnel, both ops & maintenace, to monitor the performance of the "lead" pump and pull it when worn excessively.

 

[shahyar]

thanks.Those are very useful info.

 

[jsummerfield]

In addition to the lead and lag description by cub3bead, sometimes there is a third pump. These may be labeled lead, lag and standby. As a level increases - start the lead, continued increase starts the lag and further increase starts the standby. The pumps can stop in sequence or all stop at the low operating level. Any pump exclusive combination can be selected for the lead, lag or standby.

Hand generally means that the pump is going to run. Auto could start or stop via a simple level or pressure switch instead of DCS or PLC output.

John